The movement of some plant RNA viruses is mediated by triple gene block (TGB) proteins, which cooperate to transfer the viral genome from cell to cell through plasmodesmata. Here, we investigated the function of the TGB proteins of cowpea mild mottle virus (CPMMV; genus Carlavirus, family Betaflexiviridae), which causes severe damage to soybean production. Subcellular localization experiments demonstrated that TGBp1 and TGBp3 were localized to the endoplasmic reticulum (ER), plasmodesmata (PD) and nucleus in Nicotiana benthamiana leaves. TGBp2 was unusually localized to PD. In protein interaction assays TGBp2 significantly enhanced the interaction between TGBp3 and TGBp1. Interaction assays using deletion mutants showed that the C-terminal transmembrane (TM) domain of TGBp2 is critical for its localization to PD and for its interaction with TGBp1 and TGBp3.
Soybean mosaic virus (SMV; Potyvirus, Potyviridae) is one of the most prevalent and destructive viral pathogens in the world. The P1 protein is the first N-terminal product in the potyvirus genome and shows a high sequence variability that may be related to virus adaptation to hosts. In this work, we focused on the different functions of P1 proteins in two SMV isolates SMVGZL and SMVNB during their infection of plants. Isolate SMVGZL induced weaker symptoms than SMVNB in mechanical inoculation assays, and the accumulation level of SMV CP in SMVGZL-infected leaves was lower than that in leaves infected with SMVNB, especially at the late stage of infection. The isolates SMVGZL and SMVNB had a high similarity in genome sequence except for the P1 region. P1GZL induced a higher salicylic acid (SA) response than P1NB in Nicotiana benthamiana, which may explain the lower virus titers in plants infected with SMVGZL. Our results suggest that the divergence in the P1 proteins of these SMV isolates influenced their virulence via differentially regulating SA signaling.
The bean bug (Riptortus pedestris), one of the most important pests of soybean, causes staygreen syndrome, delaying plant maturation and affecting pod development, resulting in severe crop yield loss. However, little is known about the underlying mechanism of this pest. In this study, we found that a salivary secretory protein, Rp614, induced cell death in nonhost Nicotiana benthamiana leaves. NbSGT1 and NbNDR1 are involved in Rp614‐induced cell death. Tissue specificity analysis showed that Rp614 is mainly present in salivary glands and is highly induced during pest feeding. RNA interference experiments showed that staygreen syndrome caused by R. pedestris was significantly attenuated when Rp614 was silenced. Together, our results indicate that Rp614 plays an essential role in R. pedestris infestation and provide a promising RNA interference target for pest control.
Riptortus pedestris (Fabricius), one of the major piercing‐sucking insects in soybeans, causes delayed plant senescence and abnormal pods, known as staygreen syndrome. Recent research has shown that direct feeding of this insect is the major cause of soybean staygreen syndrome. However, it remains unclear whether R. pedestris salivary proteins play vital roles in insect infestation. Here, we found that 4 secretory salivary proteins can induce cell death in Nicotiana benthamiana by transient heterologous expression. The cell death induced by Rp2155 relies on the nucleotide‐binding leucine‐rich repeat helper, HSP90. Tissue‐specificity assays indicated that Rp2155 is specifically expressed in the salivary gland of R. pedestris and is significantly induced during insect feeding. The expression of salicylic acid (SA)‐, jasmonic acid (JA)‐related genes was increased in soybean when fed by Rp2155‐silenced R. pedestris. More importantly, soybean staygreen symptoms caused by R. pedestris were significantly alleviated when Rp2155 was silenced. Together, these results suggest that the salivary effector Rp2155 is involved in promoting insect infestation by suppressing the JA and SA pathways, and it can be considered as a potential RNA interference target for insect control.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.